In order to provide a technique for reducing system noise from an output signal value (measurement data), an X-ray CT apparatus includes an X-ray generation unit that irradiates X-rays to an object, an X-ray detector that detects the X-rays transmitted through the object, a correction processing unit that corrects an output signal from the X-ray detector, and a reconstruction calculating unit that reconstructs an image on the basis of an output from the correction processing unit, in which the X-ray detector includes arranged detection elements, and in which the correction processing unit maintains an average value of output signal values of a plurality of predetermined detection elements centering on a focused detection element among the detection elements, and also reduces a variance of the output signal values of the plurality of predetermined detection elements centering on the focused detection element.
